Youngs Lake Cascades Dam Reservoir Report

Last Updated: December 15, 2025

Youngs Lake Cascades Dam, also known as Inlet Dam, is a significant earth dam located in King County, Washington, along the Tr-Cedar River.


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Summary

Built in 1950 by the local government for water supply purposes, this dam stands at a hydraulic height of 16 feet and has a storage capacity of 35,450 acre-feet. With a drainage area of 2.19 square miles and a surface area of 690 acres, this dam plays a crucial role in water resource management in the region.

Managed by the Washington Department of Ecology, Youngs Lake Cascades Dam is state-regulated, inspected, and enforced to ensure its structural integrity and safe operation. The dam is classified as having a significant hazard potential, but its condition assessment in 2019 deemed it satisfactory. Emergency action plans are in place, and regular inspections are conducted to assess any potential risks and mitigate them effectively.

For water resource and climate enthusiasts, the Youngs Lake Cascades Dam serves as a vital infrastructure supporting water supply in the region. With its impressive storage capacity and strategic location along the Tr-Cedar River, this earth dam plays a crucial role in managing water resources and ensuring the safety and well-being of the surrounding communities. The dam's state-regulated status and satisfactory condition assessment highlight the commitment to maintaining its structural integrity and mitigating potential risks for the benefit of all stakeholders involved.

Year Completed

1950

River Or Stream

Tr-Cedar River

Primary Dam Type

Earth

Surface Area

690

Hydraulic Height

16

Drainage Area

2.19

Nid Storage

35450

Structural Height

16

Hazard Potential

Significant

Foundations

Soil

Nid Height

16
       
Seasonal Comparison

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Dam Data Reference

Condition Assessment

Satisfactory
No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.

Hazard Potential Classification

High
Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.